It is known in the field of applied geophysics to prospect the Earth's crust by measuring electric voltage and current intensity. For example, for the purpose of prospecting mineral ore deposits DE 10 2007 029 782 A1 discloses a geophysical measuring method in which various prospecting methods from geophysics, such as seismic reflection technology, seismic refraction technology and resistance geoelectrical technology with boreholes, digging and an analytical approach, are combined in order to prospect a mineral deposit undergoing weathering. For the purpose of the prospecting using resistance geoelectrical technology, steel ground spikes are used as electrodes with which a current is fed into the soil by means of a voltage source so as to build up in the ground potential fields which, for example, are measured with the aid of a voltmeter. The profile and decaying of the potential fields can be used to determine a contact resistance which, as apparent conductivity or resistance is representative of the soil or the structure of the soil and the materials and structures occurring there. In the case of resistance geoelectrical technology, it is also necessary to take account of the physical processes of the induced polarization (IP effects) which, as a function of the soil present, mostly lead to a rise and decay of the measurement potential fields than the applied potential fields which occur more slowly in different ways.